The answer is mayonnaise: specifically Hellmann’s, which the nation apparently slops on everything except french fries.

Hellmann’s alone accounted for $401.2 million in sales last year, according to Businessweek — nearly a third of the total $1.3 billion mayo market here.

Heinz Ketchup is a distant third with $278.6 million in sales, edged out by the $286.2 million worth of Tostito’s salsa sold last year.

Mayo’s dominance is such that the varieties account for five of the 10 most popular condiment brands, including Best Foods and Kraft.

Kraft, for instance, offers its classic mayonnaise, as well as Miracle Whip, and flavored mayos such as reduced fat Chipotle, Garlic & Herb, Horseradish-Dijon, and regular Hot & Spicy.

According to SymphonyIRI Group, a market-research firm that analyzed the sales data, nearly 400 million containers of mayonnaise were sold in the year ending Sept. 5, 2010.

That’s compared to 271 million jars of salsa and 256 million bottles of ketchup sold nationwide.

The condiment is used so often that Americans seem to take for granted its use.

The company, founded by German immigrant Richard Hellmann in 1905, was later acquired by its chief competitor, Best Foods, in 1932.

Rather than create one master mayo, Best Foods chose to divide America up. Best Foods sold its mayo in the western half of the country, and Hellmann’s on the eastern half. As of 2000, the company is now owned by Unilever.

Although many were surprised when salsa surpassed ketchup a few years ago, it makes sense, given the diversity of the population and the increasing appetite for Mexican food, experts say.

Also, a bottle of ketchup keeps in the refrigerator a lot longer than a jar of salsa.

Mustard doesn’t show up on the list until number 7, with French’s Classic, which sold $88 million of the yellow stuff last year.

Grey Poupon, the second most popular selling mustard, accounted for $44.9 million in sales.

Salsa’s surge is a more recent development.

Frito-Lay debuted its white-corn chip Tostito’s in 1979, followed a few years later by its salsa. The brand now accounts for 37 percent of the total $764 million in salsa sales.

When one hears the word condiment, a bottle of Heinz 57 is probably the image that most often comes to mind.

The No. 1 selling ketchup brand doesn’t rack up the sales of mayo or salsa, but Heinz does account for nearly two thirds of all sales of the condiment. Hunt’s Ketchup is a distant second, accounting for $73.9 million in sales or 54 million bottles.

Next most popular after mayo, salsa, ketchup, and mustard is hot sauce, which doesn’t show up on the list until number 12.

Frank’s RedHot Sauce accounted for $43.9 million in sales last year.

The Louisiana sauce used on the original Buffalo wings was founded in 1920 and today represents just under 20 percent of all hot-sauce sales.

Here’s the spread

Top 10 best-selling condiments of 2010 in U.S. by total sales revenue:

1. Hellmann’s Mayonnaise: $401M

2. Tostito’s Salsa: $286M

3. Heinz Ketchup: $278M

4. Best Foods Mayonnaise: $175M

5. Kraft Miracle Whip Mayonnaise: $163M

6. Kraft Mayonnaise: $159M

7. French’s Classic Mustard: $88M

8. Kraft Mayo: $79M

9. Pace Salsa: $74M

10. Hunt’s Ketchup: $73M

Sources: BusinessWeek and SymphonyIRI Group. Data is for year ending September 2010.